Preparation of certain reactive phenol-aldehyde resins and their use as modifying agents for rosin



Patented May 21, 1946 PREPARATION OF CERTAIN REACTIVE PHENOL-ALDEHYDERESINS AND THEIR USE AS MODIFYING AGENTS. FOR BOSIN Ernst Fritz Siege],Elizabeth, N. 1., assignor to Reichhold Chemicals, Inc., Detroit, Mich.

No Drawing. Application December 6, 1944, Serial No. 566,948

8 Claims.-

The present invention relates to certain reactive phenolaldehydecondensation products and to a process of preparing them. It alsopertains to their use as modifying agents for rosin, rosin esters orester gums.

The invention is particularly concerned with the preparation ofthermosetting condensation products which may be best defined as Novolakpolyalcohols; These are obtained through following the procedure of myinvention, by first forming a Novolak from ordinary phenol; and analdehyde and reacting .then .the preformed Novolak with formaldehyde inthe presence of a strong alkaline catalyst at low temperature. Theresulting compound represents a Novolak in which the unoccupied reactivepositions have been partly or completely substitutedby methylol groups.

The other important feature of myinvention is that these Novolakpolyalcohols can be used very effectively to modify rosin. It issurprising to find that they form with rosin homogeneous reactionproducts although the high reactivity and the relatively large molecularsize of. a Novolak polyalcohol might lead to the assumption' that itwould rather be converted to an insoluble infusible resin instead ofundergoing a smooth chemical reaction with rosin. A poly'alcohol derivedfrom a dicyclic phenol '(dihydroxydiphenylpropane) represents thecondensation product of largest molecular size everdescribed in patent,or other literature as being useful for the modification oi rosin.

It has been known for many years that rosin and rosin esters may be verymuch improved by the incorporation of reactive phenol-formaldehydecondensation products which, by this treatment, are rendered soluble indrying oils unless soluble originally. These combined products havehigher meltingpoints, yield solutions of greater viscosity and are moreresistant to alkali and weathering than ordinary ester gum.

All phenol-aldehyde condensation products hitherto prepared for thispurpose, to the best of my knowledge, have been made from alkylatedphenols, e. g., tertiary butylphenol, phenols .re-

acted with ketones, e. g., dihydrodiphenylpropane and alkyl phenolsobtained-from coal tar or petroleum, e. g., cresols, xylenols, etc.

When straight unmodified phenol was' used either resins of Novolakcharacter were produced ent No. 259,030, Example .8, presumably a reactive phenol resol (phenol alcoholiwas used, the preparation of which wastoo vaguely described to be duplicated by anyone unfamiliar with theinventors procedure, not to mention the huge excess of formaldehyde usedin these examples (3 mols'mo're per mol of phenol than theoretically canbe combined at all). In United States Patent No. 1,623,901 and No.1,736,757 the use of 10 a reaction product from phenol, acetone andformaldehyde has been suggested for modifica- 1 tion of rosin; in theformer even all aldehydes and ketones are referred to as carbonylcompounds for reacting on .the phenolic bodies."

However, those patents do not conflict with my invention for thefollowing reasons:

1. The reaction of ketones with phenol to form an intermediatecondensation product is much slower and less complete than that ofaldehydes and therefore less-economical.

2. The present invention is limited to the use of aldehydes as'resinforming components, while nowhere in the literature 'has there beendescribed up to now a practical process for. produc- 2 5 ing straightphenol-aldehyde resin reactive-with There remain to be mentioned afewmore pat;

ents which cover certain phenol-aldehyde con-- 40 densation productsand/or the process of preparing them, although these products are notused or suggested for the modification of rosin. In United States PatentNo. 1,614,171 phenol polyalcohols are described which are made ex- 4clusively fromjmonoand dicyclic phenols." The distinct differencebetween thispatent and my own invention can be best illustratedonExample #3 of said patent. The polyalcohol disclosed therein isprepared from diphenylolethane and formaldehyde. The former is a puredicyclic phenol while the starting compound I use for the preparation ofmy polyalcohol is a Novolak., Both phenolic compounds may be obtained bythe reaction of phenol with acetaldehyde of which the Patent No.1,623,901, Example 7, and British Pa conditions are the decisive factorfor the formamass.

" of diphenylolmethane derivatives.

tion of the final product. Diphenylolethane is: a chemical individual ofthe following constitution:

on on while my Novolak represents a mixture of probably di-, tri-,tetracyclic and possibly higher complex phenolic compounds ofapproximately the following structure: a

It is obvious that the polyalcohol described in' Example #3 of theaforementioned patent'diifers from my Novolak polyalcohol in much thesame way that the dicyclic phenol diflers from my mixture of complex.phenols as shown by the formulae above.

United States Patent No. 1,699,727 is solely concerned with thepreparation of cast phenolic resins. The only similarity between thispatent 1 and my own invention is that both processes are 1 carried outin two-successive steps,v the first of which is the formation of aNovolak in either case. However, the respective products obtained 3 v inthe second step are completely different from I each other. Thepotentially reactive composition covered' by this patent consist of'Novolak, phenol, formaldehyde and a basic catalyst, preferably ammonia,while, the final product obtained by following myprocess constitutesessentially a neutral Novolak polyalcohoL- Although it is obviousthat thtwo products are clearly distinuished by their "'diiferent chemicalcomposition, it must also be emphasized that Weith's intermediateproduct does not and cannot yield a Novolak polyalcohol. during itsconversion process into "a firm jelly and finally a solid hard Phenolalcohols are obtained only by means of strong alkalis as catalysts atlowtem peratures while weak bases favor the formation Therefore, whenNovolak, phenol and formaldehyde are heated at 40 C. in the presence of.ammonia or hexamethylentatramine, as described in the pat- 2,400,718ent referred to, large molecules are formed by cross linkage of theoriginal small molecular units through methylene bridges and a jelly ora hard resin is formed. In contrast to this, when Novo-, lak isreactedwith formaldehyde at 30-40 C. in

presence of e. g. NaOH methylol groups are at tached to the reactivepositions of the phenol nuclei and the resulting-condensation product isatoms of the phenol nuclei by methylol groups.

The formation of a Novolak polyalcohol is, of course extremely importantsince its methylol groups are utmost essential for the laterrreactionwith rosin. On the other hand, Weith's product is not a polyalcohol inany phase of its conversion from a liquid intermediate to a solid and isthus useless for the particular. purpose my 1 Novolakpolyalcoholis'designed for. a

Also in United States Patent No. 1582,0553;

two step process; coveringa certain method as to manufacture castphenolic resins is described. j p

In the first step 20% of the total phenol is reactedlwith formaldehydein acid mediu'mform ing a Novolak. In the; second step the residual 80%phenol isfaddedand the resulting ixture is further reactedwithformaldehyde in alkaline medium. The inventorjdesc'ribes his secondstep 1 reaction as follows:

The whole is then boiled once mor so the new formation of resin isfinished.

The distinct differences l ietween'v the; product 4 and process ofthispatent and my own invention are principally these: 'f a I havethetotal amount'of phenol present dur-,-

ing the condensation in acid ,mediumat the end of which about 20% phenolis uncombined. The

free phenol may be removedby any. suitable means or it may remain with'the Novolak. In

the latter case it is, evident that my phenolic composition containsabout 'Novolak and about 20% phenol whenthe condensation withformaldehyde in alkaline med ium is started.

Kulas phenolic mixture containsonly about 20%.

Novolak and about 80% phenol-at the sam'estage,

of the reaction. In'otherflwords the proportion of phenol to Novolakis'Just'the reverse in the ,re-'

spective processes; It is obvious that Kulasalkaline condensationproduct for the preparation of which phenol is essentially used as thestartingl material would be quite different from mine which 7 is derivedessentiallyfrom Novolak even if the re action conditions in bothcases'were the same. However, the difference between the respectivealkaline condensation product becomes evengreater due to the: factthatthe alkaline reactions arecarried out under quite dissimilarconditions.

Those disclosed by Kulas are ver'yyaguely described although hedefinitely states that he boils his reaction mixture. In contrasttothis,

I react my Novolak with formaldehyde at a temperature not higherjthan 40C. until practically all formaldehyde is combined. Kulas hightemperature procedure yields an indefinite mix of phenol are'convertedinto polyalcohols' exclusively. That large molecules are actually formedin Kulas' second step reaction is proven by the fact that his'finalcondensation product is.

(1) Is neither a phenol- -nor a Novolak polyalcohol. (2) Is thusunsuitable for the reaction with rosin, and v (3) Lacks uniformity frombatch to batch since the given procedure is very vague.

The only known method of making phenol-aldehyde-resin-modified ester gum.of high quality is to utilize the valuable reactive methylol groupsattached to the phenol nucleus by reacting the phenol with formaldehydein strong alkaline medium at low temperature. This procedure has beenknown for years and applied as well in manufacturing processes for along time, but using only modified phenol as a resin base. The reasonswhy straight phenol has never been employed to prepare reactive aldehyderesins for modification of rosin become apparent on consideration of thevarious difiiculties its use entails. These difficulties may besummarized as follows: e

1. Phenol condensed with aqueous formaldehyde in alkaline medium at lowtemperature yields phenol alcohols which are infinitely water solubleand cannot be separated from the water without vacuum distillation. I

In case of vacuum distillation all alkali, which has to be applied in arather large quantity in order to carry out the formaldehyde combinationwithin a reasonable time at low temperature is left in the resin and hasa detrimental effect on both the condensate and its combination productwith rosin, or if neutralized. is precipitated as salt after theevaporation of water and produces turbidity in the modified rosin.Moreover, the salt cannot be washed out, due to the great watersolubility of the condensation product, as mentioned above.

3. If only a small or negligible quantity of alkali is used which mightbe left in the final phenolic condensation product, higher temperaturemust be applied in order to combine the formaldehyde completely withinareasonable time. But an elevated temperature changes the course ofreaction destroying a considerable portion of the reactive methanolgroups which undergo further reaction with phenolic bodies formingunreactive methylene bridges. Moreover, under this type of treatment thereaction mechanism becomes uncontrollable, the degree of condensationand the reactivity of the final phenolic resin being different frombatch to batch even if the same amount of formaldehyde is applied ineach instance and combined to the same extent.

The essence of my invention resides in the discovery of a novel reactivecondensation product of uniform quality derived from ordinary phenol andaldehyde exclusively and a method of preparing it which overcomes allthe aforementioned process difilculties. The invention further residesin the application of my condensation product for the modification ofrosin or ester gum which reaction has been hitherto carriedout withcondensation products derived from modified phenols. The invention gainsparticular importance from the considerations which are to follow. Itmakes possible:

l. The use of ordinary phenols which is relatively inexpensive incomparison with modified phenols, which in some casesare more than twiceas highin price as phenol itself, the unmodifled phenol being availableas a raw material base in almost any desired quantity.

2. The useof phenol in combination with aldehydesexclusively, whichundergo a much more ready and complete reaction than ketones, suggestedby some inventors previously, to, form'an intermediate condensationproduct. 1

3. The production of oleoresinous varnishes which possessbetterqualities than those in which modified phenols are used as a resin base.Nowadays when slow drying oils like linseed oil and dehydrated castoroilare displacing, more and more wood oil varnishes, my improved resinousproduct is of especially great interest because it brings the mostessential properties (e. g. bodying time, drying speed, alkali andweather resistance) of linseed oil varnishes up to the level of thoseobtained from wood oil.

My method for preparing reactive phenol-aldehyde resins derived fromstraight phenol suitable for the modification of rosin preferablycomprises the following steps: v

l. Phenol is first reacted with a part only of the total amount ofaldehyde used in the process,

which is able to combine the aldehyde within a' reasonable time may be.employed Some free phenol (about 20% of the total amount applied) whichmay be left uncombined in this stage may be distilled off by steam orunder vacuum or may remain in the Novolak and be reacted withformaldehyde in the second step. The amount of uncombined phenol, ifany, remaining at the end of this stage is in any event relatively smallas compared with the quantity of phenol initially used, so that theprincipal phenol-aldehyde reaction takes place in the first stage, whilethe principal reaction taking place in the second stage is between thepreformed Novolak formed in the first stage and formaldehyde, in thepresence of an alkaline catalyst. i

2. The preformed Novolak is further condensed at low temperatures (notexceeding 40 C.) with aqueous formaldehyde'in strong alkaline-medium toyield a Novolak polyalcohoi the methylol groups of which are of utmostimportance for the later reaction with rosin. The proportion of Novolakto formaldehyde may be varied within a wide range. Theamount offormaldehyde used in the alkaline reaction must adjust the molecularratio of total phenol groups to total aldehyde to at least 1:1, howeverI prefer to bring it within the range of 1 l.5-1:l.8. The amount ofalkaline catalyst, preferably NaOH r KOH, is so regulated that itdissolves the Novolakand the aqueous formaldehyde homogeneously andbrings,

about practically complete combination of' the reactants at lowtemperatures within a reasonable time. The reaction time is a functionof the temperature, the quantity of alkali catalyst per phenol unit andthe molecular ratio of ,phe-

when a l"\quan titative determiratitn shows the. only about 1 of theformaldehyde applied for the alkaline 5 condensation is uncombined. Atthis point'the mixture is neutralized; thereby the condensation productis settling out and can be separated from the water;h The resin iswashed with fresh water and is en ready for the reaction with rosin; Theresulting product is liquid and can easily be handled in the followingoperations leadjing'to'th'e manufacture of. phenol modified ester gum. 3Inthis way I obtain a straight phenol-aldehyde resinwhich: .7 Y v (1)Represents a highly reactive Novolak poly:- alcohol of uniform quality.i (2) Is water insoluble to a large extent and can therefore easily'beseparated from wate and freed from alkali.

ity oleoresinmls varnishes.

pared fin whichhexamethylenetetramine is incorporated as a hardeninagent, aside. from the fact that those resins would notbe useful for thecombination with rosin. e

The following. specific examples are given way of illustration and notbyway of limitation. /W Example 1 I (a) Kmixtureof 470. me; phenol, 243gms.

' aqueous formaldehyde (37% by weight) and as cc. concentrated .HC lfisheated-up to 100 C. and held for 1-2 hours until all formaldehyde hasbeen combined. Then '70 gms. NaOH (50% by Weight) are added and themixture is cooled down to 30 C. Hereupon 485 gms. formaldehyde (37% byweight) are gradually added at about 30 C.'and the mixture is then heldat this temperature until not more than 5% formaldehyde remainsvuncombined, which procedure takes about 4-5, jdays. Then neutralizationwith HCl takes place, the separated water is drained oil! and the/resinwashed with fresh water to remove the salt. i

(b) Gum'roein (M. P. about 65 C.) gra1ns 720 Phenolic resin as-preparedunder (a) con-- v taining about 17% water.- grams 107 Glycerol do 54 Theabove constituentsfwhen treated according to the well known procedure tomake phenolicresin modified ester gum yield a product of thefollowingspecifications:

Acid No I Melt poi I Viscosity (55% in toluene) l Q-R (Gardner-Heidi;tubes) 2,400,718 nolic moups to formaldehyde. .lt amounts to 2-5 Yieldsa clear. reaction product with rosin I suitable for the production'ofhigh qual- Example 2 I. c

(a) 940 gms. .phenol, 220'gms. para-aldehyde end 5 cc. concentratedHClare heated up to 100 C. and held for about 2-3 hours until mac-.-tically all aldehyde has been combined. '1hen the water-split oil'-duringv the reaction andthe phenol which remained. uncombined aredistilled of! under vacuum. The resin obtained is a Novolak. 560 gms. ofthis Novolak are dissolved gradually mixed with 405 gms. formaldehyde(37% by weight) at about 30-C. This mixture is held for 2-3 days atabout 30C. until not more than 5% formaldehyde is uncombined. Then' theresin is precipitated by neutralization with HCl. the water drained of!andthe resin freed I from salt by washing with; fresh water.

2o Gum rosin (M. P. about 65 C.) grams v product of the following con-Acid number 80 My 12s;

Viscoslty (5 5% in toluene) un r ---E,-G (Qardner-I-Ioldt tubes) Example3 (a) 470 phenol and '1l0 gmspara-alde- 5 hyde with 3 cc. concentratedH01 as a catalyst are reacted together by heating up to 100 C andholding for 2-3 hours until all'the aldehyde has been'combined. Then 70gms. of NaOI-I (50%) are added, the mass. is cooled downto about 30' 740 C. and subsequently mixed with 52031118. formaldehyde (37% byweight)../After about 3-4 days during which time the temperaturemaintained at about 30 C. all but about 5% formaldehyde hasbeencombined, the resin isseparated andwashed as indicated in Examples 1and 2.

: Gum rosin (melt point about r 65 C.) grams 720 5 Phenolic resin asdescribed under (a) containing about 22% water-"u do 147 Glycerol: do

Above constituents giveaproduct of the following specifications: a

Procedure ..he1d for d hour'5u minutes at 580,

F.-, then diluted with mineral spirits to 50% non-volatile and drieradded z e Viscosity E-I" (Gardner-Holdt tubes) Dustfr Alkali resistance(2% aqueous NaOH 7 7 :solution) 2 hours The present application is acontinuation-in-.

part of my application Serial No. 417,856; filed ,November 4, 1941. 7

While, in the foregoing specific examples, alkaline catalysts such asNaOH and KOH are given 76 by way of illustration, other alkalinecatalysts .in 235 gms. NaOH (specific gravity-1.2) and T v Aboveconstituents when treated in the usual.

ter 1 hour Tackfree after 6 hours may be employed without departing fromthe spirit oi the invention, as, for example, the alkaline earthhydroxides such as Ca(OH)r and BatOH);

Iclaim: 1. A process of producing reactive phenolaldehyde resin whichcomprises reacting exclu-' sively unmodified phenol and an aldehyde intwo successive steps: (1). forming a Novolak in acid medium using thetotal amount of phenol but only part or the totalamount of aldehyde, and(2) condensing further the intermediate Novolak with aqueousiormaidehydein a medium of strong alkali without addition 01 further phenol at atemperature not above 40 C. to convert it into a Novolak polyalcohol.

2. A process as defined in claim 1 in which the mol ratio of totalcombined aldehyde to phenol is at least 1:1 so that finally a heathardening vresin is formed.

3. A reactive phenol-aldehyde resinou condensation product rormed byreacting exclusively unmodified phenol and an aldehyde in two successivesteps which consist in first reacting the total amount of phenol withonly part of the total amount or aldehyde in an acid medium to form awater insoluble Novolak, and then condensing further the intermediatewater insoluble Novolalr with aqueous formaldehyde in a medium of strongalkali without addition 01 further phenol at a temperature not above 40C. to convert A it into a Novolak polyalcoho'l.

4. A heat-hardening reactive resinous product according'toclaim 3wherein the mol ratio of total combined aldehyde to phenol is at least1:1.

'5. A modified rosin formed by reacting the resinous product defined inclaim 3 with rosin.

6. An oleoresinous varnish formed from a dryin; oil, and an ester gumproduced by reacting the resinous product defined in claim 3 with rosinfurther-the intermediate water insoluble Novolak with aqueousformaldehyde in a medium of strong alkali in the absence of uncombinedphenol at a temperature not above 40 C. to convert it into a Novolakpolyalcohol.

ERNST FRITZ 'SIEGEL.

